System and method for alerting visually impaired users of nearby objects

ABSTRACT

A system and method for assisting a visually impaired user including an imaging device, a processing unit for receiving images from the imaging device and converting the images into signals for use by one or more controllers, and one or more vibro-tactile devices, wherein the one or more controllers activates one or more of the vibro-tactile devices in response to said signals received from the processing unit. The system preferably includes a lanyard to be worn around the neck of the user such that a first vibro-tactile device is arranged on the right side of the user&#39;s neck, a second vibro-tactile device on a left side of the user&#39;s neck, and a third vibro-tactile device at the back portion of the user&#39;s neck. The vibro-tactile devices are activated depending on a determined position in front of the user of an object and the distance from the user to the object.

FIELD OF THE INVENTION

The present invention relates to the field of object detection methodand systems for the visually impaired, and in particular, it relates toa system and method for alerting visually impaired users of nearbyobjects, especially those beyond the reach of a cane.

BACKGROUND OF THE INVENTION

Many people living with complete blindness do not leave their homeswithout a sighted person. Even those with the skill and courage to usethe long cane avoid areas with many street obstacles such as poles,planters, and benches. As a result these people can be isolated and havestrict limitations on when and where they can travel in their dailylives. Generally, when moving around, the awareness of surroundingobjects is provided by the users hearing and the sensing of objectsusing a cane. There is a need in the art for a device to alert users ofsurrounding objects, beyond the reach of a cane.

SUMMARY OF THE INVENTION

According to one embodiment of the invention, there is provided a systemfor assisting a visually impaired user comprising (a) an imaging device;(b) a processing unit for receiving images from the imaging device andconverting the images into signals for use by one or more controllers;and, (c) one or more vibro-tactile devices; wherein the one or morecontrollers activates one or more of the vibro-tactile devices inresponse to the signals received from the processing unit.

According to one aspect of the invention, the system includes a lanyardmeans sized and otherwise dimensioned to be worn around a neck of theuser, wherein the one or more vibro-tactile devices are mounted on thelanyard means. Preferably, the one or more vibro-tactile devicescomprises first, second, and third vibro-tactile devices; the firstvibro-tactile device positioned on a right side of the lanyard means,the second vibro-tactile device positioned on a left side of the lanyardmeans, and the third vibro-tactile device positioned on a top end of thelanyard means, thereby providing for a vibro-tactile device positionedat a right side of the user, a left side of the user, and at a centerposition proximate the neck of the user when the lanyard means is worn.

According to another aspect of the invention, the imaging device and theprocessing unit are mounted at a bottom end of the lanyard means suchthat the imaging device and the processing unit are positioned proximatea chest portion of the user when the lanyard means is worn.

Preferably, the imaging device includes left and right imagers; saidleft and right imagers positioned and arranged to provide stereoscopicimages to said processing unit, and the processing unit includes animage processing unit. The image processing unit is adapted to createrectified images to eliminate distortion in the images provided by theimagers and to create a depth map from the stereoscopic images

According to another aspect of the invention, the processing unitcreates a three-dimensional reconstruction based on data from the depthmap, the three-dimensional space in front of the user is divided into aplurality of volumes of space, and the processing unit determineswhether objects in front of the user reside in one or more of theplurality of volumes of space. The processing unit further produces asignal representative of the one or more volumes of space occupied bythe objects. The signal is preferably representative of a direction anddistance from the user of the objects. Preferably, the signal istransmitted to the one or more controllers which activate one or more ofthe first, second and third vibro-tactile devices in response to thesignal. The first vibro-tactile device being activated when the signalindicates the presence of the object generally to the right of the user,the second vibro-tactile device being activated when the signalindicates the presence of the object generally to the left of the user,and the third vibro-tactile device being activated when the signalindicates the presence of said object generally in front of the user.According to another aspect, the controller activates the vibro-tactiledevices with an intensity proportionate to the distance from said userof the object.

According to another embodiment of the invention, the system furtherincludes audio alert means arranged such that the controller activatesthe audio alert means when the signal indicates the presence of theobject at face level of the user.

According to another embodiment of the invention, a method for alertingvisually impaired users of nearby objects includes acquiring images froman imaging device, processing the images to generate a signal for use byone or more controllers, activating one or more vibro-tactile devices inresponse to the signal received from the one or more controllers.

According to one aspect of the second embodiment, there is providedlanyard means sized and otherwise dimensioned to be worn around a neckof the user, wherein the one or more vibro-tactile devices are mountedon the lanyard means. Preferably, the one or more vibro-tactile devicescomprises first, second, and third vibro-tactile devices; the firstvibro-tactile device positioned on a right side of the lanyard means,the second vibro-tactile device positioned on a left side of the lanyardmeans, and the third vibro-tactile device positioned on a top end of thelanyard means, thereby providing for a vibro-tactile device positionedat a right side of the user, a left side of the user, and at a centerposition proximate the neck of the user when the lanyard means is worn.

According to another aspect of the second embodiment, the imaging devicecomprises left and right imagers positioned and arranged to providestereoscopic images to said processing unit. The processing unitincludes an image processing unit and the method further includescreating rectified images to eliminate distortion in the images providedby the imagers and creating a depth map from the stereoscopic images.

According to another aspect of the second embodiment, the method furtherincludes creating a three-dimensional reconstruction based on data fromthe depth map, dividing the three-dimensional space in front of the userinto a plurality of volumes of space, determining whether objects infront of the user reside in one or more of the plurality of volumes ofspace, and producing a signal representative of the one or more volumesof space occupied by the objects, wherein the signal is representativeof a direction and distance from the user of the objects.

According to another aspect of this embodiment, the signal istransmitted to the one or more controllers which activate one or more ofthe first, second and third vibro-tactile devices in response to thesignal. The first vibro-tactile device being activated when the signalindicates the presence of the object generally to the right of the user,the second vibro-tactile device being activated when the signalindicates the presence of the object generally to the left of the user,and the third vibro-tactile device being activated when said signalindicates the presence of the object generally in front of the user. Thevibro-tactile devices may also be activated with an intensityproportionate to the distance from the user of the objects. The methodmay further include generating an audio alert when the signal indicatesthe presence of the object at face level of the user.

It is an object of this invention to partially or completely fulfill oneor more of the above-mentioned needs.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of exampleonly, with reference to the accompanying drawings, in which like numbersrefer to like elements, wherein:

FIG. 1 shows the system of the invention worn on a user;

FIG. 2 is a top schematic view of the system according to the invention;

FIG. 3 is a close up view of the system worn by the user as shown inFIG. 1;

FIG. 4 is a back view of the system worn by the user;

FIG. 5 is a flowchart showing a method in accordance with the invention;

FIGS. 6A-6D are raw and rectified images as used by the invention;

FIGS. 7A and 7B show images being processed in accordance with theinvention;

FIG. 8 shows a representative depth map in accordance with theinvention;

FIG. 9 shows a representative three dimensional space as generated inaccordance with the invention; and,

FIG. 10 shows a schematic view of the three dimensional space in frontof a user divided into volumes of space.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 to 4, the invention generally includes a system 10for assisting a visually impaired user 5 including an imaging device 20,a processing unit 30 for receiving images from the imaging device andconverting the images into signals for use by a controller 40, and oneor more vibro-tactile devices 50 activated by the controller 40 inresponse to signals received from the processing unit 30. The inventionassists a blind cane user 5 by alerting of dangers and obstacles beyondthe reach of their cane 7. The invention alerts the user of obstacles byactivating vibrating vibro-tactile devices 50 that rest on, or adjacentto, the skin of the user's neck. Preferably, the location of eachvibro-tactile device 50, and the strength of vibration from eachvibro-tactile device 50 indicates the direction and distance toobstacles, as will be explained in further detail below. The system 10is preferably portable and battery powered. As will be appreciated by aperson skilled in the art, the system 10 does not obstruct any remainingvision that a visually disabled user may have.

According to the preferred embodiment, the system 10 includes lanyardmeans 60 sized and otherwise dimensioned to be worn around a neck of theuser, in a manner similar to a necklace. The lanyard means may be formedfrom a natural rubber tubing, of the type generally referred to assurgical tubing. Electrical wiring means to connect the controller 40 tothe vibro-tactile devices 50 may be routed within the tubing.

The vibro-tactile devices 50 are mounted on the lanyard means. As shownin the illustrated embodiment, there system 10 includes first, second,and third vibro-tactile devices 52, 54, 56. The first vibro-tactiledevice 52 may be positioned on a right side of the lanyard means 60, thesecond vibro-tactile device 54 on the left side of the lanyard means 60,and the third vibro-tactile device 56 on a top end of the lanyard means60. In this manner, a vibro-tactile device 52, 54, 56 is positioned at aright side of the user 5, the left side of the user 5 and at a centreposition of the user 5, proximate the back of the user's neck when thelanyard means 60 is worn. According to the preferred embodiment, thefirst vibro-tactile device 52 is positioned at a mid-point of thelanyard means 60, the second vibro-tactile device 54 and the thirdvibro-tactile device 56 are positioned at equidistant points from thefirst vibro-tactile device 52, in opposite directions thereof, andpreferably, when worn by the user around the neck, the second and thirdvibro-tactile devices 54, 56 are arranged at an angle of approximately45 degrees from the first vibro-tactile device 52, in oppositedirections thereof. This relationship may alternately be described inrelation to a mid-point on the user's neck, with the first 52, second54, and third 56 vibro-tactile devices being arranged orthogonally toeach other such that the angle between the first vibro-tactile device 52and the third vibro-tactile device measured at the mid-point on theuser's neck is 90 degrees and similarly, the angle between the thirdvibro-tactile device 56 and the second vibro-tactile device 54 measuredat the same mid-point is 90 degrees.

The imaging device 20 and the processing unit 30 are mounted at a bottomend of the lanyard means 60 such that the imaging device 20 and theprocessing unit 30 are positioned proximate a chest portion of the user5 when the lanyard means 60 is worn. In this manner, the system 10appears as a type of neck-worn camera device and is relativelyinconspicuous. Furthermore, the system 10 is easily donned and doffedwithout assistance from other people or without complex mountingrequirements.

The vibro-tactile devices 50 are preferably manufactured by installing amotor into a housing adapted to be mounted onto the lanyard means 60.The motor, may, for example be one produced and sold by Jameco underpart number 7ZK681. Various other forms of vibro-tactile devices 50 mayalso be used. The controller is adapted to activate the motor andgenerate vibrations indicative of a distance and direction of an objectfrom the user. Other means and mechanisms for the generation ofvibration in response to a signal are known and otherwise not furtherherein described. Vibrations produced by the vibro-tactile devices 50are generated in response to a signal received by the controller 40. Thesignal from the controller 40 includes information as to the directionand distance from the user to an object.

Preferably, the location of the vibration, as dictated by one of thevibro-tactile device directs the user's attention to that direction. Theleft vibro-tactile device 54 indicates an object in front of the personto the left. The center vibro-tactile device 56 indicates an object tothe front or center direction. Likewise the right vibro-tactile device52 indicates an object to the right. The intensity of vibration of avibro-tactile device is indicative of the distance from the object tothe user. Preferably, strong vibration intensity indicates closeproximity. Medium vibration intensity indicates middle distance objects.Weak vibration intensity indicates distant objects. A lack of vibrationindicates no objects. Alternatively, rather than varying the vibrationintensity to indicate a distance to the object, a length of vibrationmay be used. Thus, longer periods of vibration may be used to indicatecloser objects and shorter periods of vibration may be indicative ofmore distant objects. Preferably, the correlation between distance andintensity of vibration (or length of vibration) will be customizable,such that a user, either on their own or with the help of a technician,can alter these settings to accommodate for a particular user'ssensitivity.

The imaging device 20 preferably comprises two camera lenses 20 a and 20b, positioned laterally spaced from each other and arranged to takestereoscopic images. The lenses 20 a and 20 b are preferably mountedwithin a housing 70 that holds the processing unit 30, controller 40,and all related hardware and power elements, such as a battery,preferably a lithium ion battery, and related hardware required totransmit signals to the vibro-tactile devices. The housing 70 preferablyincludes a cover to enclose the aforementioned elements to protect samefrom damage, for example by dust, water, or excessive impact. Accordingto one implementation of the invention, a printed circuit board 80 ispositioned within the housing and has mounted thereon the imagingdevices 20 a and 20 b, processing unit 30, controller 40 and relatedcircuitry arrangements for carrying out the invention. In a preferredembodiment, a sensor such as a 3-axis accelerometer 82 or a gyroscope,is provided to determine the rotation of the imaging devices 20 a and 20b with respect to the user. The printed circuit board will also hold amemory device 84, preferably SDRAM, but other types of memory are alsocontemplated, to store and processes images as they are taken. Variousother hardware attached to the printed circuit board or coupled theretomay be necessary to carry out the invention, including additional imageprocessors, PCI, HPI, and EMAC interfaces, power planes and decouplingcapacitors. A power supply, internal clocks, an I2C interface, videoports and various relays may be required to run the image processingsoftware as described below. An external memory interface may alsooptionally be provided.

The algorithms for use with the device and according to the method ofthe present invention will now be described. It will be understood bythose skilled in the art that these descriptions are by example only andother algorithms which perform equivalent functions may also be used.

The device of the present invention locates objects in three dimensionsbased on stereoscopic digital images, three axis accelerator (or similarsensor) readings and known geometry. Algorithms that may optionally berun include digital image correction, and stereoscopic imagecorrespondence. The following describes the step by step process fromstereo images to three dimensional reconstruction, to activation ofvibrating vibro-tactile devices according to the present invention.

Referring now to FIG. 5, in step 1, the imaging device captures twodigital images. The digital images are preferably capturedsimultaneously from the two, left and right, imagers. The two imagersare preferably spaced apart laterally, for example, at a distance ofapproximately 5 cm. It will be understood by those skilled in the artthat other orientations of the imagers and non-lateral spacingarrangements are equally within the scope of the invention. Thesecaptured images are referred to as raw images. FIGS. 6A and 6B show leftand right raw images of a street scene, respectively, as would beencountered by a typical user of the device. It will be noted that inboth raw images, the lamp post 600 in the foreground appears curved.This curvature is due to lens distortion. Objects in the left raw imagedo not match the same horizontal row in the right image. It is thereforenecessary to reduce, or eliminate, this curvature and process the imagessuch that an accurate representation of the scene may be obtained.

Referring now to FIG. 5, in step 1, the imaging device captures twodigital images. The digital images are preferably capturedsimultaneously from the two, left and right, imagers. The two imagersare preferably spaced apart laterally, for example, at a distance ofapproximately 5 cm. It will be understood by those skilled in the artthat other orientations of the imagers and non-lateral spacingarrangements are equally within the scope of the invention. Thesecaptured images are referred to as raw images. FIGS. 6A and 6B show leftand right raw images of a street scene, respectively, as would beencountered by a typical user of the device. It will be noted that inboth raw images, the lamp post 600A and 600B in the foreground appearscurved. This curvature is due to lens distortion. Objects in the leftraw image do not match the same horizontal row in the right image. It istherefore necessary to reduce, or eliminate, this curvature and processthe images such that an accurate representation of the scene may beobtained.

In step 2, the processor, and preferably the image processor correctsthe effects of lens distortion and further aligns the pair of imageshorizontally. After image processing, the new left and right images areherein referred to as the “rectified” images. FIG. 6C is a leftrectified image as processed by the device of the present invention.FIG. 6D is a right rectified image as processed by the device of thepresent invention. Note that in the FIG. 6C and FIG. 6D the lamp post600C and 600D in the foreground is no longer curved. The lamp post nowappears straight. In addition, objects in the left image now align insame horizontal image row as in the right image. Various methods ofcorrecting for lens distortion and aligning stereoscopic images areknown in the art and may be used with the invention.

Then, by matching successive images in both left and right images, adepth map is created. The depth map is an image that has the samedimensions in the plane of the screen as the rectified images, but isrepresentative of the difference in depth between images in eachpicture. The pixel value in the depth map is a value of the left toright shift of objects in the left image versus the same object in theright rectified image. An exemplary resultant depth map is shown in FIG.8. While the data held in the depth map includes a depth value for eachpixel, as represented on screen, the depth map is gray scaled, forexample, light gray represents a disparity of 5 pixels, gray representsa 20 pixel disparity and black a 0 pixel disparity. Each pixel in thedepth map holds a pixel value that represents the horizontal disparityof the matching locations in the left rectified image to the rightrectified image. For example, if a point in the left rectified image is5 pixels to the right of the corresponding object in the right rectifiedimage, then the depth map will hold the value “5” for this pixel. Thus,by comparing left and right stereoscopic images, the relative depths ofobjects can be calculated in accordance with the above description todetermine areas in the scene with objects closer and further away fromthe user.

In step 4, a three dimensional reconstruction is created based onmeasurements from the depth map. Based on individual pixel depth values,each point in the scene as represented by a pixel in the depth map isassigned a depth value, and accordingly is representative of a point inthree dimensional space. FIG. 9 is a perspective view of a scene derivedfrom depth map and according to the image processing of the presentinvention. Position 900 is the lamp post. Note that the original rightimage used to interpret the street scene is now rotated to be alignedvertically. Rotation is calculated from the data from the 3-axisaccelerometer. The three dimensional calculation uses the depth map, thecamera intrinsics, and trigonometry. This calculation is based on thefield of view of the camera lens. Camera intrisics include camera focallength, image dimensions, and camera focal center. Such calculationswill be apparent to those skilled in the art. Every point in the depthmap is given a three dimensional position in the three dimensionalreconstruction. Each of these three dimensional positions is used in thenext step of occupancy mapping.

One of the possible problems associated with the above approach is whenthe imaging devices are tilted, or become tilted as the user movesaround. To accommodate this, a three axis accelerometer may be used tocalculate the tilt of the camera. This tilt information is used torotate the three dimensional scene into the vertical or uprightorientation. Alternatively, a gyroscope can be designed into the devicefor enhanced position sensing. A three axis gyroscope would add moreaccuracy to the tilt sensing. The result of adding a three axisgyroscope to the three axis accelerometer would result in more precisesix axis orientation. The height of the camera above the ground may alsobe used in the calculations to properly place objects in the threedimensional space.

In step 5, the three dimensional space in front of the user is dividedinto three dimensional volumes, referred to herein as a collisionfrusta. Each collision frusta has a three dimensional location andorientation relative to the user. The number of three dimensional pointsin each collision frusta is then counted. In the following example, acollection of nine collision frusta is used to determine the location ofabove ground objects that are in front of the user. FIG. 10 is a topdown view of the three dimensional reconstruction. The outlines of theabove ground collision frusta are indicated at 1000. The collisionfrusta have been projected onto the two dimensional ground planes. Theletters A, B, C denote the location of the first row of three collisionfrusta closest to the camera. Collision frusta “A” is to the left. “B”is center. “C” is to the right. Letters D, E, F denote the middle row ofthe next three collision frusta. The letters G, H, and I denote thefurthest row of three collision frusta. The area 1000 is shown tooverlap both collision frusta “D” and “G”. The area 1000 in collisionfrusta “D” and “G” shows the 3D points found from the lamp post. Thelamp post thus is found to occupy collision frusta “D” and “G”.

Many other collision frusta types can be created and used for detectingspecific hazards to the user. For example a collision frusta can beadded to determine if the user is about to fall down a stairway or off arailway platform onto a railway track. In this case a collision frustacan be created to detect the presence or absence of the floor before theuser. Call this new collision frusta a “floor” collision frusta. If nofloor or sidewalk is detected in this “floor” collision frusta, it canbe assumed that the user is about to fall. The vibrations can beactivated to alert the user of this danger. Another collision frusta canbe used for alerting the user of head level obstacles. Collision frustacan be created specifically for the volume of space directly before theuser's head. Let us call this the “head” collision frusta. When threedimensional points in the three dimensional reconstruction are found tobe in head collision frusta, then the user can be alerted to this dangerby activation of the vibrating motors.

In an alternate embodiment, a speaker adapted to emit a beeping sound isincluded in the system 10. In order to alert the user of head levelobstacles, the speaker emits a beep. In this manner, a heightened senseof urgency is provided to head level obstacles and to differentiate fromthe directional indicators provided by the vibro-tactile interfaces. Inthis manner, a clear distinction is provided between head levelobstacles and other obstacles located in front of the user.

In step 6, the occupancy of collision frusta from three dimensionalpoints is determined. A determination of the occupancy of the collisionfrusta is done based on the number of three dimensional points found tolie in each collision frusta. To do this a count is made for eachcollision frusta to keep track of the number of three dimensional pointsthat are within the bounds of the collision frusta. The threedimensional points in the three dimensional reconstruction are comparedto the bounds of each collision frusta in turn. If a three dimensionalpoint is found to be within the bounds of a collision frusta, then thecount for that collision frusta is incremented. There can be manyarbitrarily shaped collision frusta. The three dimensional frusta can beof any shape. A three dimensional point can be found to be within thebounds of more than one frusta. For example, if the number of threedimensional points in Frusta “D” be greater than a minimum number, say1000, then Frusta “D” will be deemed to be “occupied”. The table belowshows an example of collision frusta occupancy. The table below showsthat collision frusta “D” and “G” are occupied. The table also shows howthe example collision frusta A, B, C, are laid out before the person.

COLLISION FRUSTA left center right far row G - occupied by H I lamp postmiddle row D - occupied by E F lamp post near row A B C

In step 7, the vibro-tactile device speed control is set based on thecollision frusta occupancy. This allows the degree of vibration to beset depending on the distance of the detected objections. Once thecollision frusta occupancy has been computed, then this occupancy ismapped to vibro-tactile device speed by a controller. Each of the threevibro-tactile devices, the left, right and center can be turned on oroff. Each vibro-tactile device can have its speed controlled by pulsewidth modulation of the power leads.

In the following example there are nine collision frusta. One example ofhow to determine to activate a vibrating vibro-tactile device can bedone by a one to one match of collision frusta occupancy to speed andlocation. The table below shows which of the three vibrating interfacesis activated at particular speeds. Motors speed can be off, low, medium,or high speed.

left center right far row G = left low H = middle low speed I = rightlow speed speed middle D = left medium E = middle medium F = rightmedium row speed speed speed near A = left high B = middle high speed C= right high speed row speed

When more than one collision frusta are occupied then a prioritydecision is preferably made. For example, a near collision frusta haspriority over a far collision frusta. Center grid collision frusta havepriority over a left or right grid location. There are many possibleways to map collision frusta occupancy to motor control. They can bechanged by the manufacturer by changing computer software. Also, futureimplementations will have user controls to allow the user to performthis function.

In step 8, the user sensors the vibrations of the vibro-tactile devicesand responds accordingly.

Upon activation vibrations in the vibro-tactile device in the neck strapare produced. The user is now alerted to an obstacle. In the currentexample this is a lamp post that is both directly in front and slightlyto the left front. As the user walks down the street the vibro-tactiledevices are updated continuously. The new settings are based on the newcaptured images. In one embodiment, the speed of the vibro-tactiledevice is updated eight times per second.

This concludes the description of a presently preferred embodiment ofthe invention. The foregoing description has been presented for thepurpose of illustration and is not intended to be exhaustive or to limitthe invention to the precise form disclosed.

What is claimed is:
 1. A method for alerting a visually impaired user ofcollision or falling hazards, the method comprising: acquiring a firstimage and a second image, of a space in front of said user, by twospaced-apart imagers; deriving, from said first image and said secondimage, a three-dimensional reconstruction comprising a plurality ofthree-dimensional points; dividing said space in front of said user intoa plurality of collision frusta each having a three-dimensional locationand an orientation relative to said user, for detecting one of: apresence of objects proximate a head of said user and an absence of afloor ahead of said user; determining one of: said presence of objectsproximate said head of said user and said absence of said floor ahead ofsaid user, based on counting a number of said plurality ofthree-dimensional points in each one of said plurality of collisionfrusta; and activating one or more vibro-tactile devices, in aparticular way, in response to said determining; wherein said pluralityof collision frusta comprises: a right collision frustum, a centercollision frustum, and a left collision frustum, each representing acorresponding right, center, and left portion of said space in front ofsaid user, respectively; and wherein said one or more vibro-tactiledevices, comprise a right, a center, and a left vibro-tactile devices,and wherein said activating one or more vibro-tactile devices comprisesone of: activating said right vibro-tactile device in response to saiddetermining in said right collision frustum, activating said centervibro-tactile device in response to said determining in said centercollision frustum, and activating said left vibro-tactile device inresponse to said determining in said left collision frustum.
 2. A methodfor alerting a visually impaired user of collision, the methodcomprising: acquiring a first image and a second image, of a space infront of said user, by two spaced-apart imagers; deriving, from saidfirst image and said second image, a three-dimensional reconstructioncomprising a plurality of three-dimensional points; dividing said spacein front of said user into a right collision frustum, a center collisionfrustum, and a left collision frustum, each having a three-dimensionallocation and orientation, relative to said user; further dividing eachof said right collision frustum, said center collision frustum, and saidleft collision frustum into three collision frusta to provide a nearright collision frustum, a near center collision frustum, a near leftcollision frustum, a medium right collision frustum, a medium centercollision frustum, a medium left collision frustum, a far rightcollision frustum, a far center collision frustum and a far leftcollision frustum, said frusta being relative to said user; determininga presence of one or more objects proximate said user, based on countinga number of said plurality of three-dimensional points in each one of:said near right collision frustum, said near center collision frustum,said near left collision frustum, said medium right collision frustum,said medium center collision frustum, said medium left collisionfrustum, said far right collision frustum, said far center collisionfrustum and said far left collision frustum; when an object isdetermined to be present in adjacent collision frusta, a prioritydecision is made; and activating one of: a left, a center, and a rightvibro-tactile device, in a particular way, based on said prioritydecision.
 3. A method according to claim 2, wherein said prioritydecision comprises prioritizing a near collision frustum over a mediumcollision frustum, and prioritizing a medium collision frustum over afar collision frustum.
 4. A method according to claim 2, wherein saidpriority decision comprises prioritizing a center collision frustum overboth a left collision frustum and a right collision frustum.
 5. A methodaccording to claim 3 wherein activating one of: said left, center, andright vibro-tactile devices, in a particular way, comprises activatingone of: said left, center, and right vibro-tactile devices at a lowspeed, a medium speed, or a high speed based on said priority decision.6. A method according to claim 3 wherein activating one of: said left,center, and right vibro-tactile devices, in a particular way, comprisesactivating one of: said left, center, and right vibro-tactile devicesfor a short duration, a medium duration, or a long duration based onsaid priority decision.
 7. A method according to claim 5 whereinactivating one of said left, center, and right vibro-tactile devices, ata particular speed comprises one of: activating one of: said leftvibro-tactile device, said right-vibro-tactile device, and said centervibro-tactile device, at a high speed, if said priority decisionindicates said presence of said one or more objects in a correspondingone of: said near left collision frustum, said near center collisionfrustum, and said near right collision frustum; activating one of: saidleft vibro-tactile device, said center vibro-tactile device, and saidright vibro-tactile device, at a medium speed, if said priority decisionindicates said presence of said one or more objects in a correspondingone of: said medium left collision frustum, said medium center collisionfrustum, and said medium right collision frustum; and activating one of:said left vibro-tactile device, said right-vibro-tactile device, andsaid center vibro-tactile device, at a low speed, if said prioritydecision indicates said presence of said one or more objects in acorresponding one of: said far left collision frustum, said far centercollision frustum, and said far right collision frustum.
 8. A methodaccording to claim 2 wherein said activating said left, center, or rightvibro-tactile devices, comprises: activating said left vibro-tactiledevice if said priority decision indicates said presence of said one ormore objects in one of: said near left collision frustum, said mediumleft collision frustum, and said far left collision frustum; activatingsaid center vibro-tactile device if said priority decision indicatessaid presence of said one or more objects in one of: said near centercollision frustum, said medium center collision frustum, and said farcenter collision frustum; and activating said right vibro-tactile deviceif said priority decision indicates said presence of said one or moreobjects in one of: said near right collision frustum, said medium rightcollision frustum, and said far right collision frustum.
 9. A system forassisting a visually impaired user comprising: a first imager and asecond imager spaced apart producing a first image and a second image ofa space in front of said user; a processing unit: receiving said firstimage and said second image, and deriving from said first image and saidsecond image a three-dimensional reconstruction comprising a pluralityof three-dimensional points, dividing said space in front of said userinto a plurality of collision frusta each having a three-dimensionallocation and an orientation relative to said user for detecting one of:a presence of objects proximate a head of said user and an absence of afloor ahead of said user, and determining one of: said presence ofobjects proximate said head of said user and said absence of said floorahead of said user based on counting a number of said plurality ofthree-dimensional points in each one of said plurality of collisionfrusta; and one or more controllers activating one or more vibro-tactiledevices, in a particular way, in response to said determining by saidprocessing unit; wherein said plurality of collision frusta comprises: aright collision frustum, a center collision frustum, and a leftcollision frustum, each representing a right, a center, and a leftportion of said space in front of said user, respectively; and whereinsaid one or more vibro-tactile devices, comprise a right, a center, anda left vibro-tactile devices, and wherein said activating one or morevibro-tactile devices comprises: activating a right vibro-tactile devicein response to said determining in said right collision frustum,activating a center vibro-tactile device in response to said determiningin said center collision frustum, and activating a left vibro-tactiledevice in response to said determining in said left collision frustum.